Recently, many researchers have been applied zeolitic materials for dye wastewater treatment by adsorption method because of more practical and economical without requiring a lot of solvents. However, the presence of natural zeolite is limited and only available in a specific area. In this research, pumice stones containing the main components of silicate and aluminate were used as an alternative material to synthesize zeolite. The ability of pumice and zeolite was also tested for adsorbing one of cationic dyes, namely methylene blue (MB). Zeolites were synthesized through the hydrothermal method in high pH conditions and characterized by Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD). The characterization results revealed that the addition of an alkaline solution changed the molecular structure of pumice into Na-P1 zeolite and caused differences in dye adsorption capacity. The adsorption efficiency of pumice was only achieved 65.83% with the MB uptake as much as 5.89 mg/g at the MB concentration of 50 mg/L for 24 hours, while the Na-P1 zeolite was able to adsorb MB molecules almost 100% with the uptake capacity up to 9.12 mg/g.

Patchouli or Pogostemon cablin benth is one of the most important essential oil-producing plants in Indonesia. In the world of trade, patchouli oil is widely used as raw material, a mixing agent, and a fixative. Patchouli oil can be upgraded to Hi-Grade Patchouli (HGP) with a Patchouli alcohol (PA) content of 40-80% through vacuum distillation technology. Furthermore, HGP can be further processed into crystal patchouli with a purity of up to 90-100%. This study aims to improve the quality of patchouli oil produced by the community. This study examines the effect of variations in vacuum pressure on the distillation process on the quality of the resulting patchouli oil, determines the impact of cooling temperature variations on the resulting crystal mass, and determines the crystal quality (patchouli alcohol content and crystal size). The method used was vacuum redistillation followed by crystallization of patchouli oil. In the redistillation stage, it is carried out using a rotary vacuum evaporator. Redistillation is conducted in two stages: the first is to produce a light fraction at a temperature of 125 ℃, and the second is to produce a heavy fraction at a temperature of 140 ℃. The variable that was varied was process pressure. The pressure used is 1; 2-3; 6-8 and 10-12 mbar. The process is continued with crystallization using the cooling method (cooling crystallization) with a cooling temperature variation of -12 ℃ and -15 ℃. The results showed that through the vacuum redistillation method, the quality of patchouli oil produced by the community could be increased in PA levels up to 81.79%. The lower the operating pressure, the highest the quality of patchouli oil is produced. The lower the crystallization cooling temperature, the more crystal mass is formed. The crystal purity of this HGP resulted in very high levels of crystalline PA, namely 99.6%. The crystal size obtained is 290-600 μm on average.

The preparation of activated carbon as an adsorbent from biomass waste was usually conducted at high temperatures. In this research, activated carbon was prepared from palm kernel shell by the pyrolysis process at temperature under 400 °C to reduce excessive energy consumption. This study aims to identify the surface character of the formed activated carbon as an adsorbent for methylene blue. The pyrolysis process produced activated carbon which has a hydroxyl (3102–3423 cm−1) and carboxyl (1650 cm−1) functional groups, resulting in ionic interactions between activated carbon and methylene blue. The equilibrium data fit the Langmuir isotherm model with correlation efficient higher than 0,99. The highest adsorption capacity is 0.28 mmol/g adsorbent for activated carbon which is hydrolyzed at 350 °C with a surface area of 523 m2/g adsorbents.

This study presents the comparison of methylene blue (MB) adsorption using alkali-activated pumice from Bali (A-P1) and Banten (A-P2). Pumice samples were activated under alkaline solution and followed by simple hydrothermal treatment in a polypropylene bottle at 100 °C for 24 hours. The X-ray diffraction (XRD) patterns showed that both treated pumices have different peak characteristics, where only A-P1 was dominated by the mineral phase of GIS-NaP1 zeolite. The change of amorphous to zeolite phases increased negative sides and caused A-P1 to have a higher adsorption capacity than A-P2. Based on the adsorption data of AP1 and AP2, the Langmuir isotherm model shows a better fit with high correlation values (R2) compared to the Freundlich model. This means the interaction between the treated pumice and MB followed the assumption of monolayer coverage on homogeneous surfaces, in which the maximum values of MB adsorption were found to be 51.546 mg/g for A-P1 and 27.027 mg/g for A-P2. In addition, A-P1 and A-P2 were also potentially used as heterogeneous catalysts for MB degradation through Fenton-like process due to the presence of iron oxide contents.

Caesalpinia sappan L., known as sappan wood, has been extensively explored by many researchers because it contains various structural types of phenolic compounds. This study objectives are to investigate the effect of pH on the flourescent color of carbon dots (CDs) from sappan wood and its application as an acid-base indicator under UV light for the first time. CDs were synthesized through the hydrothermal route in ethanol solvents. The synthesized CDs were further characterized by UV-Vis spectrophotometry, fluorescence and Fourier Transform Infrared (FT-IR) spectroscopy. Based on the results, CD solutions performed multiple flourescent colors (yellow, orange and green) under UV light at 365 nm when the pH was adjusted to be 1, 3, 5, 7, 9 and 11. These multiple colors were produced because of the instability of phenolic compounds in the sample, especially brazilin which was easily oxidized to brazilein in alkaline condition. According to the FT-IR spectra, the most prominent differences of the sample before and after the treatment process was observed in the peak region ranging from 1500-1700 cm-1. The characteristic band of carbonyl groups was identified at 1697 cm-1 in the treated sample (pH 9), but it was unobserved in the spectrum of sappan wood and the treated sample (pH 5). The presence of carbonyl group can be assumed that brazilin has been oxidized to brazilein after the alkaline treatment process and making the flourescent color was gradually shifted from yellow to green. Under normal light, the sappan wood�s extract and CD solution produced yellow and red colors in acidic and alkaline conditions, respectively. However, only CD solutions which have yellow, orange and green emissions in different pH conditions under UV light. Therefore, the synthesized CDs can be used as an acid-base indicator in both different light conditions.